Modern postal/shipping scales have the capability of calculating postal and/or shipping charges based on the sensed weight of a parcel or mailpiece and rate information contained on electronic look-up tables resident in the scale. The look-up tables are typically stored within programmable read-only memories and accessed by a microprocessor within the scale.
One type of look-up table that may be stored in a PROM is a "zip-to-zone" (hereinafter, ZZ) table. In the proper mode of operation, an operator would enter via a keyboard, a postal zip code for a shipping destination point, and the scale would automatically determine the shipping zone associated with that zip code. It has been determined that the first three digits of a postal zip code provide sufficient resolution for zip-to-zone conversion. It has also been determined that there need only be on the order of one hundred different look-up tables, each containing subtables related to a group of three digit zips to cover the entire range of possible shipping origination points.
Another type of look-up table that may be stored in a PROM is a "rate" table. A Rate-PROM provides charge-perzone data to the microprocessor. Based on the destination zone, which may be entered either directly by the operator or supplied via the ZZ-PROM, and the data in the Rate-PROM, the microprocessor is able to determine the shipping charge for a parcel. Typically, a Rate-PROM having United Parcel Service (UPS) rate tables and a Rate-PROM having United States Postal Service (USPS) rate tables are used in a scale. Sometimes, the five-digit zip code, rather than the zone only, is required to determine the shipping charge.
A specific type of Rate-PROM is an "alternate carrier" (hereinafter, AC) PROM. An AC-PROM provides the microprocessor with zone charge data for a carrier other than UPS or USPS. Conveniently, the zone structure, but not the charge per zone, is the same for many of these alternate carriers. When it is desired by a shipper to select from a plurality of alternate carriers, a plurality of PROM-based alternate carrier look-up tables would be required.
Sometimes, a shipper may desire to transport a shipment of articles to a point remote from the origination point, and ship from the remote point. Thus, it is convenient to have "drop ship" (hereinafter DS) PROMs resident in the scale and selectable by the user to determine the zip-to-zone conversion based on the remote, drop ship point. A DS-PROM is simply the ZZ-PROM associated with the remote shipping origination point. Having several DS-PROMs resident in the scale would be somewhat consumptive of space.
As an alternative to having a plurality of AC-PROMs and several DS-PROMs resident in the scale, it is known to provide interchangeability for the PROMs. This is typically achieved by providing a connector rack comprising a number of slots in the scale, and by providing the associated PROMs on circuit boards (hereinafter, PROM boards) that plug into the connector rack. As alluded to hereinbefore, size constraints limit the number of slots available in the connector rack. For example, although there may be a total of nine slots in a connector rack, three may be occupied by PROMs programmed for control functions, one by a United States Postal Service Rate-PROM, one by a United Parcel Service Rate-PROM, and one for a shipping origin point ZZ-PROM--leaving only three slots available for AC-PROMs and DS-PROMs.
Due to the data storage capability of modern, inexpensive PROMs, it is quite feasible to provide four distinct alternate carrier rate look-up tables on a single 64 kilobyte (k) PROM. Each rate table for different alternate carriers may be located in a different 16 k portion of a single 64 k AC-PROM. Furthermore, it is possible to provide two AC-PROMs per board. This addresses the problem of providing for a plurality of alternate carrier look up tables on a single AC-PROM board, and it is well known how to access each look-up table individually. However, the benefit of providing several different AC look-up tables on a single PROM board is offset by the complexity involved when a particular carrier, or carriers, changes rates.
Similarly, it would be technically feasible to provide more than one DS look-up table on a single PROM board. Again, for providing access to several DS look-up tables, two DS-PROMs could be provided on each PROM board. This however would create a virtual nightmare in terms of creating and stocking in inventory all of the combinations of possible PROM boards having, for instance, two DS look-up tables. Even with three digit zip code resolution and grouping into approximately only one hundred distinct zip-to-zone look-up tables, nearly five thousand different PROM boards having two DS-look-up tables would be required.
Thus, it is an object of the present invention to provide an efficient technique for user selection of a plurality of AC-PROMs and/or several DS-PROMs, efficient in the sense of keeping to a minimum the number of distinct PROM boards required in inventory, while maintaining ease of customer characterization of the functions within a particular scale.